Abstract: A retaining device for axial piston machines embodies a shoe plate with a plurality of openings radially disposed in it. On each side of each opening a substantially flat portion exists to maintain a tangential line of radial contact with the shoes. The shoe plate has a force transferring portion made up of a plurality of raised surfaces. The raised surfaces are arranged to apply two areas of axial contact on each shoe. The two areas of axial contact are generally diametrically opposed which keeps the shoes in sliding contact with the swash plate and thus substantially eliminates tipping of the shoes.

Abstract: A method is provided for producing a piston assembly adapted for use in a hydraulic pump or motor and having an overall length shorter than previously known piston assemblies while maintaining a strong mechanical connection and a high, efficient volumetric output. The method includes the steps of forming a slipper with a spherical ball on one end; forming a piston having a body portion and a connecting portion, the connecting portion having a spherical bottom surface, a groove spaced from the bottom surface and a contoured portion having an angled outer surface and an inner surface; inserting the spherical ball into the cavity; forcing the contoured portion inwardly to place the inner surface into contact with the spherical ball and to substantially longitudinally align the outer surface of the piston body with the angled surface of the contoured portion; heat treating the piston to a predetermined hardness and depth; and finishing the total longitudinal length of the piston to a finished size.

Abstract: An apparatus and method is provided for producing a piston assembly for use in a fluid translating device such as a hydraulic pump or motor. In the subject arrangement, a piston is provided having a cavity at one end thereof and a slipper having a spherical head portion which is precisely positioned within the cavity to provide a space therearound and subsequent thereto a plastic material is formed in the space to maintain the spherical head portion in the cavity. This arrangement eliminates the sliding friction that exists in other piston assemblies and furthermore reduces the precise sizing of the cavity relative to the spherical head portion.

Abstract: Piston assemblies for use in fluid translating devices normally are made of hardened metal alloy materials which require very smooth surface and are always subject to varying degrees of thermal expansion when being operated at high operating temperatures. In the subject arrangement, a piston assembly is provided and is constructed of most, if not all, ceramic components. The piston assembly includes a ceramic piston having a spherical head portion at one end thereof which rests in a spherical cavity of a ceramic slipper and held therein by a cylindrical ring. The cylindrical ring can be of a one-piece or a two-piece design which is in contact with the spherical head portion and bonded to the ceramic slipper, thus, retaining the spherical head portion. The cylindrical ring could also be made of a metallic material. The metallic ring is bonded to the ceramic slipper and subsequently swaged to hold the spherical head portion within the spherical cavity.

Abstract: Axial piston fluid translating units commonly experience undesirable shaft deflections and barrel tilting during operation. A fluid translating unit includes a barrel plate interposed the end of a barrel and a porting surface defined within a housing thereof. The barrel plate is axially spaced from an end of the barrel and is in face sealing engagement with the porting surface. The barrel plate defines a plurality of fluid ports, each communicating between one of a plurality of barrel cylinder bores and the porting surface. In one aspect a plurality of counterbores are provided in the barrel in surrounding relation to the fluid ports. A plurality of seal rings having a sealing end defining an annular seal face of a predetermined width for face sealing engagement with the barrel plate. The seal rings are each disposed in one of the counterbores in circumferential sealing relation of a predetermined length which is no greater than the width of the sealing face.

Abstract: Hydraulic piston pumps and motors are used in various applications to power implements, steering, propel, and auxiliary systems. However, it is important to keep the piston weight and compressible fluid volume low in order to have a smaller more efficient pump. The subject piston is manufactured in a simple manner to achieve a reliable, light weight design. The piston has a cylindrical body having an outer surface. The piston is manufactured by forming a first bore having a large diameter in the body extending from the outer surface and terminating at an annular shoulder. A second bore is formed which extends from the annular shoulder to a predetermined depth. A tube is inserted through the bore and extends a predetermined distance into the second bore. A cap has a bore and is positioned on the body in abutment with at least a portion of the outer surface. The cap slidably receives the tube through the bore.

Abstract: Variable displacement axial piston pumps are useful in outputting pressurized fluid to operate fluid actuators. The currently available center pivoted variable displacement axial piston pumps waste energy by compressing trapped volumes of oil during operation. The present variable displacement axial piston pump has first and second opposite sides of a swash plate pivotally connected to a pump housing by a pair of off-center pivots with the angle of the swash plate being controlled by first and second actuators connected to the opposite sides of the swash plate. Each of the off-center pivots includes a pair of pivot pins connected to the housing and releasably pivotally seated in a pair of semi-cylindrical pockets formed in the opposite sides of the swash plate. The first actuator at the first side of the swash plate holds the semi-cylindrical pocket seated against the pivot pin while the second actuator controls pivotal movement of the swash plate about the first off-center pivot.

Abstract: The design and construction of seals located between a cylinder barrel and a barrel plate rotatable therewith for axial piston fluid translating units have caused an increase in overall unit size, increased stiffness between the barrel and barrel plate and an increase in manufacturing cost and complexity. The present invention overcomes these problems by providing an axially compact, combined circumferential and axial face seal means. The seal means includes an annular seal ring having a sealing end and a biasing end with the sealing end defining an annular seal face of a predetermined width. A biasing means is attached to the biasing end of the seal ring and includes a spring ring having a generally flat base plate with a plurality of resilient fingers angularly extending therefrom. The axially compact structure of the seal means of this invention provides the required flexibility between the barrel and barrel plate while reducing overall unit size, and cost and complexity of manufacturing.

Abstract: A balanced free-planet drive mechanism includes a reaction ring gear, an output ring gear, an input sun gear arranged along a central axis, and a plurality of floating planet elements individually having a first planet gear engaged with the sun gear, a second planet gear engaged with the output ring gear, and a third planet gear engaged with the reaction ring gear. A required first rolling ring gear resists radially inward movement of the planet elements adjacent the third planet gear, and an optional second rolling ring gear resists radially inward movement of the planet elements adjacent the first planet gears to maintain the planetary elements essentially parallel to the central axis. A plurality of ring segments are connected to the output ring gear and engage a groove in each of the planet elements to maintain the planet elements in a preselected axial position and to transmit relatively low thrust forces.

Abstract: Electro-hydraulic valve arrangements are useful in controlling a displacement control member of a variable displacement pump or motor. However, previous digital electro-hydraulic valves having brief pulse widths required special high speed solenoids to speed up the response time of the valve and resulted in increased cost of the valve. The subject digital electro-hydraulic valve arrangement includes a pair of on/off solenoid actuated valves arranged in series so that a flow path is initiated by a first of the valves and is disrupted by the second valve. The response times of the valves are equal such that directing an electrical signal to the second valve during the response time of the first valve results in extremely brief pulse widths of the valve arrangement. Using two solenoid actuated valves in this manner permits the use of less costly solenoid valves to provide very brief pulse widths through the total valve arrangement.

Abstract: In a pump or fluid motor (11, 11a, 11b) having a closed chamber (57) in which cylinders (38) orbit and reciprocate, leakage and cooling fluid which accumulates in the chamber (57) is formed into a rotating annular volume by centrifugal effects and exhibits a higher pressure in the region where the cylinders (38) move radially inward and closer together than in the opposite region where the cylinders (38) move outward and further apart. Power wastage from drag torque, turbulence and heat generation is reduced by scavenging the accumulated fluid from the chamber (57). Internal recirculation of the scavenged fluid from the high pressure portion of the annular rotating volume back to the low pressure portion is avoided by communicating the drain passages (68, 68a, 68b) with only a limited relatively high pressure sector of the rotating volume of fluid.

Abstract: A radial piston device such as a radial piston motor (10) has a rotor assembly (34) rotatably positioned within a cylindrical race (43) which is movable to a first displacement position by a first piston (52) and a second displacement position by a second piston (53). A pintle (26) extends into a bore (36) of a rotor (33) of the rotor assembly (34) and has first and second ports (27,28) for delivering fluid to and from the rotor (33). In order to reduce the size of the radial piston device and to minimize the number of external lines, a control valve (66) is positioned within a bore (59) of the pintle (26) and selectively controls fluid flow from one of the first and second ports (27,28) to the first and second pistons (52,53) for shifting the cylindrical race (43) between the first and second positions.

Abstract: In a radial piston pump-radial piston motor drive system, a centrifugal replenishing pump is provided integral with the pump driving means. The radial-piston pump, radial piston motor, centrifugal replenishing pump, and most of the fluid circuit, including fluid sump are all contained within a unitary housing to provide a compact self-contained pump-motor hydrostatic unit.

Abstract: A fluid device has an inlet and a pumping chamber which is positioned in spaced relation to the inlet. The chamber is rotatably movable relative to the inlet. Apparatus is provided for contacting the fluid at the inlet at a preselected angle sufficient for accelerating the fluid into the chamber.

Abstract: A combination shuttle and high pressure relief valve is provided within a hydrostatic drive or transmission system. The valve is constructed with a spool member in two sections. The sections include hooks that interact with one another to lock the spool sections together in one mode of operation, yet permitting the spool sections to act independently in another mode of operation. Complete fluid charging of the fluid system is ensured by dual flow circuitry between the system pump and motor, while a restrictor valve means is connected to the shuttle and pressure relief valve to provide continuous flow of fluid through a system filter.

Abstract: A radial piston pump comprises a housing having a drive shaft rotatably mounted therein and a rotor operatively connected to the shaft for rotation therewith. A pintle valve is mounted in the housing and the rotor is rotatably mounted thereon for communicating fluid from an inlet of the housing to an outlet thereof. A plurality of circumferentially spaced and radially extended pistons are mounted on the rotor with each of the pistons having a cylinder reciprocally mounted on an end thereof for pumping purposes. The inlet communicates with an inlet side of the pintle valve via a single inlet passage which communicates unrestricted fluid flow therethrough.

Abstract: The invention is concerned with an improvement in a control system for a hydrostatic drive of a vehicle comprising a pair of hydrostatic pumps the output of each of which is adjustable by moving an arm attached to a servo valve controlling the displacement of said pumps, each pump powering a respective hydraulic motor which drives a respective ground engaging means of said vehicle. The improvement of the present invention mechanically controls the speed and steering functions of the system.